The present invention relates generally to methods of testing super hard materials. More specifically, the present invention relates to methods of testing super hard materials used as cutters in earth drilling applications.
Super hard materials are commonly used in down-hole drilling operations that require cutters to penetrate hard and abrasive earthen formations. Polycrystalline diamond (PCD) is a super hard material commonly used in the manufacture of cutters for use in such operations. PCD cutters typically comprise diamond material formed on a supporting substrate (typically a cemented tungsten carbide (WC) substrate) and bonded to the substrate under high temperature, high pressure (HTHP) conditions.
A limiting factor to effective drilling is the wear on such cutters, so attention has been directed at designing cutters that are more wear resistant. Cutters may be subjected to abrasion tests to determine optimal cutter specifications.
One such abrasion test is disclosed in U.S. Pat. No. 5,833,021 to Mensa-Wilmot et al., which is herein incorporated by reference for all that it contains. Mensa-Wilmot discloses a test that is used to assess the life of a cutter called the granite log abrasion test which involves machining the surface of a rotating cylinder of Bane granite. To assess the cutter, one determines a wear ratio of the volume of log removed relative to the volume of cutting tool removed.
Another test is disclosed in U.S. Pat. No. 6,003,623 to Miess, which is herein incorporated by reference for all that it contains. Miess discloses a test where a cutter was used to cut Sierra white granite mounted on a vertical turret lathe to present a flat rotating surface of rock to the cutter. The cutter was mounted with a negative back rake such that its central axis formed a 5 degree angle with a line normal to the planar surface of the stone. The turret lathe was adjusted to advance the cutter radially toward the center of the stone as the stone was rotated below the cutter. The surface speed was 30 inches per second, the feed rate was 0.125 inches per revolution, and the coolant was water.